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Contrary to a recent report [Rinder et al.: Blood 82:505, 1993], aspirin does inhibit the release of alpha-granule contents as well as inhibiting the release of dense granule contents by human platelets during ADP-induced aggregation in citrated platelet-rich plasma (PRP). Measurements were: percent release of 14C-serotonin from prelabeled platelets, radio-immunoassay of beta-thromboglobulin (beta TG), and expression on the platelet surface of the alpha-granule constituent,
P-selectin
, by flow cytometry. During the second phase of ADP-induced aggregation, 69.0 +/- 8.3% of beta TG and 54.1 +/- 4.6% of 14C-serotonin were released (mean +/-
SEM
, n = 13); aspirin treatment reduced these values to 6.0 +/- 1.2 and 1.0 +/- 0.3%, respectively. In contrast, incubation of platelets with ADP without stirring caused only 6.7 +/- 1.7% release of beta TG and 2.1 +/- 0.4% release of 14C-serotonin; these low values were not appreciably affected by aspirin. During ADP-induced primary aggregation in PRP anticoagulated with FPRCH2CI (PPACK), only 4.7 +/- 0.9% release of beta TG and no detectable release of 14C-serotonin occurred; aspirin had no effect. In both stirred and unstirred PRP, the thrombin receptor activating peptide, SFLLRN (50 microM), caused at least 75% release of the contents of both granules, which was partially inhibited by aspirin. Upon incubation of platelets with ADP (2-10 microM), the mean fluorescence intensity due to
P-selectin
was < 14% of that induced by SFLLRN. In this unstirred system used for flow cytometry, aspirin treatment caused no significant inhibition of
P-selectin
expression. Thus, under conditions in which ADP does not cause secondary aggregation (physiological Ca2+ concentration or unstirred citrated PRP) release of the contents of both types of granules is less than 7% and aspirin is not inhibitory; the
P-selectin
expression associated with this low percent release is also unaffected by aspirin. However, aspirin does strongly inhibit the extensive release of both alpha-granule and dense granule contents during ADP-induced secondary aggregation in citrated PRP.
...
PMID:Conditions influencing release of granule contents from human platelets in citrated plasma induced by ADP or the thrombin receptor activating peptide SFLLRN: direct measurement of percent release of beta-thromboglobulin and assessment by flow cytometry of P-selectin expression. 870 47
Leukocytes attach to and roll on inflamed endothelium and on leukocyte monolayers that form on the endothelial cells. Leukocyte-leukocyte interactions occurring under hydrodynamic shear stress are mediated by binding of L-selectin to unknown sialomucin-like glycoproteins. We show that purified neutrophil PSGL-1, a sialomucin glycoprotein that serves as a ligand for both P- and E-selectin, can also support the attachment and rolling of free flowing neutrophils in vitro. Neutrophil rolling on PSGL-1 was abolished by the anti-L-selectin mAb DREG200 and by the anti-PSGL-1 mAb PL1, indicating that L-selectin can interact directly with PSGL-1. Neutrophil rolling on neutrophil monolayers was also blocked by PL1 (60 +/- 9%
SEM
inhibition); however, DREG200 blocked more efficiently (93 +/- 7%
SEM
inhibition), suggesting that other L-selectin ligands may exist on the neutrophil surface. These studies demonstrate that PSGL-1 on the neutrophil surface is a major functional ligand for L-selectin. The avidity of this L-selectin-dependent adhesion event was sufficient to allow individual neutrophils rolling on
P-selectin
to capture free flowing neutrophils, which progressed to form linear strings and discrete foci of rolling neutrophils. Neutrophil accumulation on
P-selectin
accelerated with time as a result of neutrophil-assisted capture of free flowing neutrophils. When neutrophil-neutrophil interactions were blocked by DREG200, neutrophils accumulated on
P-selectin
in a random pattern and at a uniform rate. Thus, leukocyte-assisted capture of flowing leukocytes may play an important role in amplifying the rate of initial leukocyte recruitment at sites of inflammation.
...
PMID:Neutrophil-neutrophil interactions under hydrodynamic shear stress involve L-selectin and PSGL-1. A mechanism that amplifies initial leukocyte accumulation of P-selectin in vitro. 878 68
To examine the hypothesis that surface
P-selectin
-positive (degranulated) platelets are rapidly cleared from the circulation, we developed novel methods for tracking of platelets and measurement of platelet function in vivo. Washed platelets prepared from nonhuman primates (baboons) were labeled with PKH2 (a lipophilic fluorescent dye), thrombin-activated, washed, and reinfused into the same baboons. Three-color whole blood flow cytometry was used to simultaneously (i) identify platelets with a mAb directed against glycoprotein (GP)IIb-IIIa (integrin alpha 11b beta 3), (ii) distinguish infused platelets by their PKH2 fluorescence, and (iii) analyze platelet function with mAbs. Two hours after infusion of autologous thrombin-activated platelets (
P-selectin
-positive, PKH2-labeled), 95 +/- 1% (mean +/-
SEM
, n = 5) of the circulating PKH2-labeled platelets had become
P-selectin
-negative. Compared with platelets not activated with thrombin preinfusion, the recovery of these circulating PKH2-labeled,
P-selectin
-negative platelets was similar 24 h after infusion and only slightly less 48 h after infusion. The loss of platelet surface
P-selectin
was fully accounted for by a 67.1 +/- 16.7 ng/ml increase in the plasma concentration of soluble
P-selectin
. The circulating PKH2-labeled,
P-selectin
-negative platelets were still able to function in vivo, as determined by their (i) participation in platelet aggregates emerging from a bleeding time wound, (ii) binding to Dacron in an arteriovenous shunt, (iii) binding of mAb PAC1 (directed against the fibrinogen binding site on GPIIb-IIIa), and (iv) generation of procoagulant platelet-derived microparticles. In summary, (i) circulating degranulated platelets rapidly lose surface
P-selectin
to the plasma pool, but continue to circulate and function; and (ii) we have developed novel three-color whole blood flow cytometric methods for tracking of platelets and measurement of platelet function in vivo.
...
PMID:In vivo tracking of platelets: circulating degranulated platelets rapidly lose surface P-selectin but continue to circulate and function. 887 31
To clarify the early involvement of cellular adhesion molecules in human glomerulonephritis, we investigated
P-selectin
and high endothelial venules' (HEVs) marker MECA-79 expression in kidney specimens by immunohistochemical and in situ hybridization analyses, and measured serum and urinary soluble
P-selectin
levels by enzyme-linked immunosorbent assay. In normal controls,
P-selectin
and MECA-79 expression were negative in glomeruli (N = 4), and serum soluble
P-selectin
levels were 114.3 +/- 36.8 ng/ml (mean +/-
SEM
, N = 12). Soluble
P-selectin
was not detectable in urine of all cases. In proliferative glomerulonephritis involving rapidly progressive glomerulonephritis (N = 6), IgA nephropathy (N = 26), lupus nephritis (N = 7) and acute glomerulonephritis (N = 2), both glomerular and interstitial
P-selectin
expression were up-regulated. Glomerular
P-selectin
expression correlated positively with local cellular accumulation, endocapillary proliferation and CD41b (platelet) staining. Interstitial
P-selectin
expression showed a positive correlation with the grade of local cellular infiltrates.
P-selectin
mRNA signals detected by in situ hybridization were only observed on capillary or venous endothelium in the interstitium, but not in glomeruli. In addition, MECA-79 was expressed on the plump endothelial cells at the cortico-medullary junction (outer medulla). Serum soluble
P-selectin
levels were significantly higher in patients with proliferative glomerulonephritis, especially in glomerular and interstitial
P-selectin
positive staining, and correlated with glomerular endocapillary proliferation. These observations suggested that
P-selectin
was associated with both glomerular and interstitial leukocyte accumulation in human glomerulonephritis, and might be expressed by two distinct mechanisms that are the activated platelets in glomeruli and the de novo expression in the interstitial lesions that correlated with MECA-79 expression as HEVs like vessels, and serum soluble
P-selectin
may be a useful marker for predicting in situ
P-selectin
expression associated with glomerular endocapillary proliferation in nephritis.
...
PMID:In situ expression and soluble form of P-selectin in human glomerulonephritis. 932 45
Soluble (s)
P-selectin
, sE-selectin, sL-selectin and soluble intercellular adhesion molecule-1 (sICAM-1) levels were examined by monoclonal antibody-based enzyme immunoassay on serum samples taken from nine patients with acute myocardial infarction (AMI) and eight patients with stable angina pectoris (SAP) before and after the successful percutaneous transluminal coronary angioplasty (PTCA). In patients with acute phase of AMI, the levels (mean +/-
SEM
) of sP-selectin (110 +/- 18 ng/ml) and sE-selectin (54 +/- 15 ng/ml) before PTCA, were significantly higher than those in the SAP group, the values being 44 +/ 27 and 21 +/- 4 ng/ml (p < 0.05), respectively. After recanalization, the levels of sE-selectin and sL-selectin were significantly decreased (sE-selectin 54 +/- 15 to 42 +/- 11 ng/ml, sL-selectin 1104 +/- 106 to 891 +/- 59 ng/ml, P < 0.05, respectively). These findings suggest that the presence of activated and/or injured endothelial cells, which may be involved in the plaque disruption or intraluminal thrombosis in AMI region and that the inflammatory process may be altered after reperfusion therapy.
...
PMID:Soluble form of selectins in blood of patients with acute myocardial infarction and coronary intervention. 954 64
The mechanism behind the development of vascular complications of hypertension in the young human remains unclear. To explore the role of vascular endothelium-generated nitric oxide (a known mediator of leucocyte-platelet-endothelial interactions) in this context, we investigated markers of endothelial activation (soluble vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1),
P-selectin
, E-selectin), and von Willebrand factor and the plasma level of the endogenous nitric oxide inhibitor asymmetric dimethyl arginine (ADMA) in a group of 31 (17 male, mean age 9.4 years) hypertensive and 9 (4 male, mean age 9.1 years) healthy, normotensive children and young adults. We found raised levels of ADMA (mean (
SEM
) 235 (32) n mol/l) and VCAM-1 (median (range) 1237 (675-2700) ng/ml) in the plasma of hypertensive subjects compared with those of normotensives (ADMA, 103 (7) n mol/l and VCAM-1, 1005 (425-1650) ng/ml, respectively). Furthermore, in hypertensive subjects, higher VCAM-1 concentrations (r = 0.66, p < 0.001) and vWF concentrations (r = 0.37, p = 0.04) were significantly associated with a higher plasma ADMA level. Therefore, an isolated increase in plasma VCAM-1 in hypertensives in association with raised ADMA may signify a selective "non-inflammatory" endothelial activation triggered by endothelial nitric oxide synthase inhibition. Since VCAM-1 is implicated in the origins of atherosclerosis, ADMA may be an important contributory factor in increasing the risk of atheroma formation in hypertensive children and young adults.
...
PMID:Vascular endothelial cell activation associated with increased plasma asymmetric dimethyl arginine in children and young adults with hypertension: a basis for atheroma? 1085 1
The impact of high frequency oscillatory ventilation (HFOV) compared with intermittent mandatory ventilation (IMV) on oxygenation and pulmonary inflammatory response was studied in a surfactant depleted piglet model. After establishment of lung injury by bronchoalveolar lavage, piglets either received HFOV (n =5) or IMV (control; n = 5) for eight hours. PaO(2) was higher and mean pulmonary arterial pressure (MPAP) was lower with HFOV (HFOV versus control, mean +/-
SEM
; endpoint PaO(2): 252 +/- 73 versus 68 +/- 8.4 mm Hg; p < 0.001; MPAP: 22 +/- 2.3 versus 34 +/- 2.5 mm Hg; p < 0.01). mRNA expression of interleukin (IL)-1 beta, IL-6, IL-8, IL-10, TGF-beta 1, Endothelin-1, and adhesion molecules (E-selectin,
P-selectin
, ICAM-1) in lung tissue was quantified by real time PCR normalized to beta-actin and hypoxanthine-guanine-phosphoribosyl-transferase (HPRT). mRNA expression of all cytokines and adhesion molecules/HPRT was higher in controls (e.g.: HFOV versus control, mean +/-
SEM
; IL-1 beta/HPRT: 1.6 +/- 0.3 versus 23.1 +/- 8.6 relative units (RU), p < 0.001; IL-8/HPRT: 8.5 +/- 2.0 versus 63.5 +/- 15.2 RU, p < 0.001). IL-8/HPRT gene expression was quantified in microdissected single cells. With HFOV, IL-8 gene expression was highly reduced in alveolar macrophages: 10 +/- 3.4 copies IL-8 mRNA/copy HPRT mRNA versus 356 +/- 142; p < 0.05 (bronchiolar epithelial cells: 33 +/- 16 versus 208 +/- 108; alveolar septum: 2.1 +/- 1.3 versus 26 +/- 11; bronchiolar smooth muscle cells: 1.3 +/- 0.3 versus 2.8 +/- 1.0; vascular smooth muscle cells: 0.7 +/- 0.3 versus 1.1 +/- 0.4). In conclusion, HFOV improved oxygenation, reduced pulmonary arterial pressure and attenuated pulmonary inflammatory response.
...
PMID:High frequency oscillatory ventilation suppresses inflammatory response in lung tissue and microdissected alveolar macrophages in surfactant depleted piglets. 1466 53
Adhesion molecules play an important role in the development and course of coronary atherosclerosis. In this study, soluble forms of vascular cell adhesion molecule (VCAM-1) intercellular adhesion molecule-1 (ICAM-1), E-selectin and
P-selectin
were evaluated in patients with various clinical presentations of coronary atherosclerosis and compared them to those with angiographically documented normal coronary arteries. Venous plasma samples were collected from 43 patients with acute myocardial infarction (AMI), 45 with unstable angina pectoris (UAP), 34 with stable angina pectoris (SAP) and 29 subjects with normal coronary arteries (control). The VCAM-1 level was significantly higher in patients with AMI (mean +/-
SEM
; 799.8 +/- 26.3 ng/ml) than those with UAP (644.2 +/- 26.7 ng/ml) and SAP (526 +/- 32.5 ng/ml) and controls (270 +/- 26.8 ng/ml). In patients with UAP, VCAM-1 was found to be significantly elevated as compared to the SAP group and controls. VCAM-1 level was also higher in SAP group than the controls. Serum levels ICAM-1 were similar among patients with AMI (424.1 +/- 15.2 ng/ml), UAP (403 +/- 12.3 ng/ml) and SAP (381.2 +/- 16.2 ng/ml); however, levels of ICAM-1 was significantly elevated in these groups as compared to the controls (244.3 +/- 11). The mean level of E-selectin was not different in AMI and UAP groups (47.2 +/- 2.2 vs. 42.6 +/- 2.1 ng/ml; respectively). However, it was significantly higher in acute coronary syndrome groups as compared to SAP (33.4 +/- 2.3 ng/ml) and control subjects (30.7 +/- 1.9 ng/ml). Serum levels of E-selectin were similar in SAP group and controls. For
P-selectin
, no significant difference was observed between AMI and UAP groups (187.5 +/- 7.2 vs. 181.7 +/- 4.7 ng/ml; respectively), however, it was significantly higher in both groups as compared to SAP group (146.1 +/- 7.4 ng/ml) and controls (108 +/- 6.6 ng/ml). Serum level of
P-selectin
was significantly higher in patients with SAP than the control group. In conclusion, determination of serum VCAM-1, E-selectin and
P-selectin
levels seems more useful for detecting coronary plaque destabilization.
...
PMID:Levels of soluble adhesion molecules in various clinical presentations of coronary atherosclerosis. 1526 39
Tissue factor (TF) is the physiological initiating mechanism for blood coagulation. Platelets play an important role in monocyte TF expression, thrombosis and inflammation. Aspirin, clopidogrel and cilostazol, which inhibit platelet responses by different mechanisms, are widely used in patients with arterial diseases. We tested the hypothesis that platelet-inhibiting agents inhibit the levels of circulating TF procoagulant activity (TF-PCA) in patients with peripheral arterial disease (PAD). Twenty-six patients with lower extremity PAD, average age 65.9 +/- 8.4 years (mean +/-
SEM
), were studied at baseline and following sequential two-week treatment regimens with aspirin (325 mg daily), clopidogrel (75 mg daily) or a phosphodiesterase inhibitor cilostazol (100 mg twice daily) singly, and with each possible combination of these agents. Circulating TF-PCA in whole blood, and plasma factor VIIa, prothrombin fragment F1.2, thrombin-antithrombin complexes (TAT), and
P-selectin
were measured. Baseline TF-PCA levels in the patients were elevated (131 +/- 19 U/ml) compared to control subjects (23 +/- 2, p < 0.0001). TF-PCA levels declined following treatment with clopidogrel alone, and with combinations of clopidogrel with aspirin or cilostazol, with the lowest levels being with the triple-drug combination. Plasma
P-selectin
declined in all treatment groups. No changes were noted in plasma factor VIIa, F1.2 or TAT. In conclusion, treatment of PAD patients with antiplatelet agents decreases circulating TF, a molecule with prothrombotic and proinflammatory effects. These findings suggest an unrecognized mechanism, beyond inhibiting aggregation responses, for the efficacy of antiplatelet drugs in patients with arterial diseases.
...
PMID:Effect of antiplatelet agents clopidogrel, aspirin, and cilostazol on circulating tissue factor procoagulant activity in patients with peripheral arterial disease. 1713 67
We investigated the effect of atorvastatin monotherapy and combined treatment with atorvastatin and pioglitazone on intima-media thickness, vascular function and the cardiovascular risk profile. In all, 148 patients (76 male, 72 female; aged 61.4+/-6.5 years; body mass index [BMI] 29.2+/-4.1 kg/m2; mean +/- SD) with increased cardiovascular (CV) risk factors were randomised. Intima-media thickness (IMT), the augmentation index (Aix@75), the microvascular response to acetylcholine (LDF), lipid status, and plasma levels of intact proinsulin, adiponectin, interleukin-6 (IL-6), monocyte chemotactic protein-1 (MCP-1), matrix metalloproteinase-9 (MMP-9), sCD40L,
P-selectin
, tissue plasminogen activator (t-PA) and blood lipids were monitored over six months. Atorvastatin treatment, alone and in combination with pioglitazone, revealed a significant regression in IMT (0.923+/-0.013 to 0.874+/-0.012 mm and 0.921+/-0.015 to 0.882+/-0.015 mm; mean +/-
SEM
; p<0.05 respectively) and Aix@75 (27.3+/-1.2 to 25.9+/-1.4; and 25.6+/-1.4 to 24.8+/-1.7%; p<0.05). The endothelial response to acetylcholine as measured by laser Doppler fluximetry (LDF) improved during combined treatment (373+/-57 to 576+/-153 AU; p<0.05). Addition of pioglitazone to atorva-statin resulted in significant further effects on high-sensitivity C-reactive protein (hsCRP), t-PA,
P-selectin
, adiponectin, triglycerides and high-density lipoprotein (HDL) cholesterol (p<0.05 respectively). Atorvastatin significantly improved IMT and vascular elasticity. Co-administration of pioglitazone provided additional effects on endothelial function, lipid profile and laboratory markers of inflammation.
...
PMID:Investigation of the vascular and pleiotropic effects of atorvastatin and pioglitazone in a population at high cardiovascular risk. 1895 40
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